Heterogeneous Single-photon Switch and Transistor with Rydberg atoms

The development of practical quantum networks and scalable photonic quantum information processing crucially depends on the ability of executing coherent, conditional operations between photons of different wavelengths. Although many optical operations are implemented using probabilistic linear-optical schemes, such approaches are typically limited to identical photons. Rydberg atomic systems provide a powerful platform for achieving strong photon–photon nonlinearities. Here, by harnessing the strong Rydberg blockade within a cold atomic ensemble, we demonstrate all-optical control of interactions between freely propagating photons of two different wavelengths. This capability serves as the foundation for implementing fundamental photonic devices at the single-quantum level. We report the realization of a single-photon switch and a photonic transistor, where a single gate photon at 795 nm controls the transmission of subsequent target photons at 780 nm. Our devices exhibit exceptional performance, achieving an extinction ratio of $\epsilon= 0.09(3)$ for the switch and a gain of G=26(2) for the transistor.This work establishes a direct pathway toward building frequency-multiplexed quantum interfaces, a key component for interconnecting disparate physical platforms in future hybrid quantum networks.